1. Field of the Invention
This invention relates generally to systems used to cool computer hardware and more particularly to an embedded heat pipe in a hybrid cooling system.
2. Description of the Background Art
FIG. 1 is an isometric view illustrating a prior art cooling system 100 used to cool heat-generating electronic devices in a computer system, such as a graphics processing unit (GPU). As shown, cooling system 100 characteristically includes a blower/fan 106, fins 109 and a bottom plate 111. Typically, cooling system 100 is thermally coupled to the GPU, for example using thermal adhesive or grease having thermal properties that facilitate transferring heat generated by the GPU to the bottom plate 111. Cooling system 100 may also include a heat sink lid (not shown), which, among other things, prevents particles and other contaminants from entering blower/fan 106 and air blown from blower/fan 106 from escaping cooling system 100. The heat sink lid, together with the fins 109 and the bottom plate 111, define a plurality of air channels 108.
Blower/fan 106 is configured to force air through air channels 108 over bottom plate 111 such that the heat generated by the GPU transfers to the air. The heated air then exits cooling system 100, as depicted by flow lines 114, thereby dissipating the heat generated by the GPU into the external environment. This process cools the GPU, preventing the device from overheating during operation. Persons skilled in the art will understand that air channels 108 typically are configured to direct air blown from blower/fan 106 over bottom plate 111 and into the external environment in a manner that most efficiently removes heat from the GPU.
FIG. 2 is a schematic diagram illustrating a computer system 200, such as a desktop, laptop, server, mainframe, set-top box, and the like within which a conventional cooling system 100 for cooling the GPU 216 is incorporated. As shown, computing device 200 includes a housing 201, within which a motherboard 204 resides. Mounted on motherboard 204 are a central processing unit (CPU) 206, a processor cooler 208 for cooling CPU 206, a system fan 210 for removing heat from computing device 200 and one or more peripheral component interface (PCI) cards 212, each interfaced with a slot located in the back part of housing 201. Motherboard 204 further incorporates a graphics card 202 that enables computing device 200 to rapidly process graphics related data for graphics intensive applications such as gaming applications. Graphics card 202 comprises a printed circuit board (PCB) upon which a plurality of circuit components (not shown), such as memory chips and the like, are mounted. In addition, graphics card 200 includes GPU 216, mounted to one face of graphics card 202, for processing graphics related data.
Because the computational requirements of GPU 216 are typically quite substantial, GPU 216 tends to generate a large amount of heat during operation. If the generated heat is not properly dissipated, the performance of GPU 216 degrades. For this reason, cooling system 100, which is configured to remove heat from GPU 216, is coupled to GPU 216.
One drawback of these conventional blower/fan cooling systems is that, as processors become more powerful and generate more heat, the fan has to be operated at very high speeds to generate the airflow through the air channels and over the heat sink necessary to cool the processor. High speed operation tends to produce a substantial amount of unwanted acoustic noise, which is annoying to users of a computer. Also, in some instances, these types of conventional cooling systems may not even be able to meet the heat dissipation requirements of certain high-performance processors. Further compounding these issues is the fact that, while processors are becoming more powerful, the available space for cooling systems within computing devices is generally not increasing. Thus, substantial improvements in the efficiency of cooling systems are required to maintain pace with the evolution of processors.
Liquid cooling systems are beginning to emerge as a viable alternative to conventional blower/fan cooling systems. A liquid cooling system dissipates heat at a much greater rate than a comparable air cooling system. However, typical liquid cooling systems are driven by large pumps, which are prone to frequent failure and tend to consume a great deal of power. Moreover, such systems tend to use large quantities of liquid, circulating at a high flow rate, and therefore must be frequently replenished or replaced.
To overcome some of these challenges, a hybrid cooling system is disclosed in U.S. patent application Ser. No. 10/822,958, filed on Apr. 12, 2004 and titled, “System for Efficiently Cooling a Processor,” which is herein incorporated by reference. FIG. 3 is an isometric view of such a hybrid cooling system 300. Similar to the system 100, the hybrid cooling system 300 may be adapted for use in any type of appropriate computing device. As shown, hybrid cooling system 300 may include, without limitation, a fansink 302 and a hybrid cooling module 304. As described in further detail below, fansink 302 and hybrid cooling module 304 may operate independently or in combination to dissipate heat from a processor or other heat-generating device within the computer system.
Fansink 302 is configured in a manner similar to cooling system 100 of FIG. 1 and includes, without limitation, a fan 308, walls 306 and a bottom plate 318. Cooling system 300 also includes a heat sink lid 320, which, among other things, prevents particles and other contaminants from entering fan 308 and air blown from fan 308 from escaping system 300. Heat sink lid 320, together with walls 306 and bottom plate 318 of fansink 302, define a plurality of air channels 322.
Hybrid cooling module 304 is adapted to be integrated with fansink 302. Hybrid cooling module 304 is thermally coupled to a portion of bottom plate 318 and includes, without limitation, a liquid channel 312, an inlet 314, an outlet 316 and a plurality of air channels 310. Hybrid cooling module 304 is coupled to a pump, which is adapted for circulating a heat transfer liquid (e.g., water or any other liquid suitable for transferring heat) through a closed loop that includes liquid channel 312. As shown in FIG. 3, the pump circulates liquid from hybrid cooling module 304 through a heat exchanger prior to supplying the liquid back to hybrid cooling module 304. Inlet 314 and outlet 316 are configured for respectively supplying and removing the heat transfer liquid to liquid channel 312. Air channels 310 are adapted for coupling to air channels 322 and for transporting forced air from fan 308 to the local environment. Air channels 310 are positioned over and around liquid channel 312 such that liquid channel 312 is substantially enclosed within air channels 310.
When cooling a processor or other heat-generating device, fan 308 forces air through air channels 322 of the fansink 302 and air channels 310 of the hybrid cooling module 304 such that the heat generated by the processor transfers to the air as the air passes over bottom plate 318. The heated air then exits system 300, as depicted by flow lines 324, thereby dissipating the heat generated by the processor into the local environment. In addition, as previously described, the pump circulates the heat transfer liquid through liquid channel 312 of hybrid cooling module 304, and heat generated by the processor transfers to the circulating heat transfer liquid as well as to air in air channels 310. Liquid channel 312 is adapted for transporting heat transfer liquid through a downstream heat exchanger, which dissipates heat from the heat transfer liquid into the local environment.
Fansink 302 and hybrid cooling module 304 may be implemented independently or in combination to dissipate heat from a processor, in order to dissipate heat from the processor in the most efficient manner. For example, fansink 302 may be implemented to dissipate a majority of the generated heat, hybrid liquid cooling module 304 may be implemented to dissipate a smaller quantity of heat, and the proportions of heat dissipated by fansink 302 and hybrid cooling module 304 may be dynamically adjusted. Alternatively, one of fansink 302 and hybrid cooling module 304 may be implemented as a primary means for heat dissipation, while the other mechanism is implemented on an as-needed basis to dissipate excess heat.
One drawback to using the hybrid cooling system 300 is that, when the pump is inoperative and no heat transfer liquid is circulated through the liquid channel 312, a substantial amount of cooling capacity is lost because air cooling provided by the fansink 302 is limited to the air channels 310, 322 that are not obstructed by the liquid channel 312. In other hybrid cooling system configurations, the fansink and the liquid cooling module may be “stacked” such that the fansink is disposed on top of the hybrid cooling module. In such configurations, when the pump is inoperative and no heat transfer liquid is circulated through the liquid channel, the standing liquid in the liquid channel acts like an insulator and retards the heat transfer between the processor or other heat-generating device and the walls of the fansink air channels, substantially decreasing the cooling efficiency of the hybrid cooling system. In addition, when such a “stacked” hybrid cooling system is installed in a peripheral component interconnect (PCI) slot, height restrictions become a concern. Consequently, the height of the fansink air channels may be reduced to allow the system to fit within the allocated space. Reducing the height of the air channels reduces the effective heat transfer area of the air channels, further decreasing the cooling efficiency of the hybrid cooling system.
As the foregoing illustrates, what is needed in the art is a way to increase the efficiency of hybrid cooling systems, especially when the liquid cooling portion of the system is not being used.